Spectrophotometric and atomic absorption determination of Ni(II) in fresh and sea waters after preconcentration by flotation

A highly selective and sensitive procedure for flotation separation followed by spectrophotometric determination, confirmed by AAS, of Ni(II) traces is proposed. The maximum flotation separation (100%) is achieved at approximately 25 degrees C in the pH range of 1-3 using sodium diethyldithiocarbamate (as a collector) and oleic acid surfactant. The floated (1 : 2) colored complex is measured spectrophotometrically at 430 nm over a concentration range of 0.5-4.0 microg/g with a molar absorptivity of 0.44 x 10(4) L mol(-1) cm(-1). The procedure was successfully applied for the separation and determination of Ni(II) in fresh and sea waters.     

Selective flotation-separation and spectrophotometric determination of cadmium using phenanthraquinone monophenythiosemicarbazone.

A simple, selective and sensitive procedure is described for the preconcentration by flotation followed by spectrophotometric determination of trace amounts of Cd(II). Cadmium forms an intense red 1:2 complex with phenanthraquinone monophenylthiosemicarbazone (PPT) at pH > or = 6. The colored Cd-PPT complex was floated quantitatively with oleic acid (HOL) surfactant at pH 6.5, exhibiting maximum absorbance at 520 nm and having a molar absorptivity of 2.4 x 10(5) L mol(-1) cm(-1). The stability constant of the formed complex is 1.5 x 10(12); log K = 12.2. Beer's law was obeyed over the concentration range 0.01-0.34 mg/L. The Sandell sensitivity and relative standard deviation are 0.4 ng/cm2 and 2.6%, respectively. The results obtained spectrophotometrically were compared to those obtained by AAS analysis. The analytical parameters affecting flotation and hence determination have been thoroughly investigated. The proposed procedure was successfully applied to the determination of Cd(II) traces in certified and real human hair samples as well as in natural waters. The structure of the complex formed and the mechanism of flotation were proposed.     

Flotation-spectrophotometric determination of trace of germanium with isochromatic dye ion-pairs formed by rhodamine 6G and tetrabromofluorescein

A flotation spectrophotometric method for the determination of germanium with isochromatic dye ion-pairs is described. The molar ratio of germanium to rhodamine 6G to tetrabromofluorescein is 1:5:5. The apparent molar absorptivity is 5.8 x 10(5) l mol(-1) cm(-1) at 531 nm. Beer's law is obeyed over the concentration range of 5.0 x 10(-8)-1.25 x 10(-6) mol l(-1). The proposed method is sensitive and accuracy and can be applied satisfactorily to the determination of germanium in vegetables.     

Determination of thallium(I) by flotation-spectrophotometric method using iodide and rhodamine B.

A method for the trace amount determination of Tl(I), via its preconcentration, is proposed. The method is based on the reaction of iodide, Tl(I) and Rhodamine B in a weakly acidic medium. In this process an ion-associated complex is formed, which is floated at the interface of aqueous-cyclohexane layers. Various amounts of Tl(I) by a subsequent separation and dissolution of the floated complex in methanol could be determined, spectrophotometrically. Beer's law was obeyed for the Tl(I) content in the range of (0.8-8.0) x 10(-7) mol l(-1) with a correlation coefficient of 0.9974. The conditional molar absorptivity was found to be 1.0 x 10(6) l mol(-1) cm(-1) at 560 nm, which indicated the considerable sensitivity of the procedure. The detection limit (DL) was 4.7 x 10(-8) mol l(-1) and the RSD (n = 5) for 4 x 10(-7) mol l(-1) of Tl(I) was 3.34%. None of the alkaline cations was interfered, and the interference of many other metal ions was eliminated via ion-exchange separation using a cation-exchanger resin, Amberlite IR-120, before the flotation step. The reliability of the procedure was confirmed by determining the Tl(I) contents of synthetic laboratory waste water by both flotation spectrophotometry and graphite furnace atomic absorption spectrometry (GFAAS). The recovery was 92.3-95.4% for 1 x 10(-7) and 4 x 10(-7) mol l(-1), respectively. The precision and accuracy of the results were comparable via F and t tests at the 95% confidence level.     

Spectrophotometric determination of thorium in standard samples and monazite sands based on the floated complex of thorium with N-hydroxy-N,N′-diphenylbenzamidine and thorin

A selective and sensitive spectrophotometric method for the determination of Th(IV) has been based on the reaction with thorin and subsequent extraction of the red-orange coloured complex with N-hydroxy-N,N'-diphenylbenzamidine (HDPBA) in benzene as floated complex at pH 2.2. The complex in ethanol exhibits a maximum absorbance at 495 nm, with a molar absorptivity of 6.0x10(4) l mol(-1) cm(-1), with a Sandell's sensitivity of 3.9x10(-3) microg cm(-2). The method follows Beer's law up to 3.0 microg Th(IV) ml(-1). None of the common cations and anions tested interfere. The detection limit of the method is 0.04 microg Th(IV) ml(-1), the RSD (n=10) is 1.4%. The method has been successfully employed for the determination of thorium in various standard and monazite samples.     

Reaction of mercury(II) and xylenol orange-III: determination of microamounts of mercury

Xylenol Orange and mercury(II) react in the presence of various bases, such as hexamine, pyridine and ammonia, to form ternary complexes, which conform to Beer's law. The 1:1:1 Hg(II)/XO/ base complex at pH 6.1 has an absorption maximum at 590 nm and a molar absorptivity of 2.2 x 10(5) l.mole(-1).cm(-1). In the absence of the base the Hg(II)(XO)(2) complex at pH 7.5 and 580 nm has a molar absorptivity of 1.7 x 10(5) l.mole(-1).cm(-1). Interferences are discussed.     

Spectrophotometric and atomic absorption determination of ramipril, enalapril maleate and fosinopril through ternary complex formation with molybdenum (V)-thiocyanate (Mo(V)-SCN)

Three different sensitive and accurate spectroscopic procedures were developed for the determination of three angiotensin-converting enzyme inhibitors, namely, ramipril, enalapril maleate and fosinopril. The first two spectrophotometric (extractive and non-extractive) procedures were based on ternary complex formation with molybdenum(V) thiocyanate. The formed complex can be determined by extraction with chloroform measured at lambdamax 517 nm Beer's law was obeyed in the concentration range from (10--90 microg ml(-1)) for ramipril and fosinopril and (4--36 microg ml(-1)) for enalapril maleate with molar absorptivity 1.2x10(4), 2x10(4) and 3.4x10(4) l mol(-1) cm(-1), respectively, or by direct measurement after addition of benzalkonium chloride as surfactant and measuring the formed ternary complex at lambdamax 545 nm with a linear relationship in the concentration range from (8-7-2 microg ml(-1)), (3--27 microg ml(-1)) and (8--72 microg ml(-1)) for ramipril, enalapril maleate and fosinopril with molar absorptivity 1.5x10(4), 5x10(4) and 2.1x10(4) l mol(-1) cm(-1), respectively. The third procedure is atomic absorption measurement through the quantitative determination of molybdenum content of the complex. These methods hold their accuracy and precision well when applied to the determination of ramipril, enalapril maleate and fosinopril in their dosage forms.     

Spectrophotometric determination of nickel with p-acetylarsenazo

A spectrophotometric method for the determination of trace amounts of nickel is described. At pH 6, nickel reacts with p-acetylarsenazo to form a 1:2 coloured complex with an absorption maximum at 630 nm. The apparent molar absorptivity is 6.5 x 10(4) l.mol(-1) . cm(-1) . Beer's law is obeyed over the concentration range of 0-0.8 microg/ml. The proposed method is selective, sensitive and can be applied to the determination of nickel in aluminum alloy.     

Spectrophotometric determination of molybdenum with 7,8-dihydroxy-4-methylcoumarin and cetyltrimethylammonium bromide

The 1:2 complexes formed between molybdenum and 7,8-dihydroxy-4-methylcoumarin in the presence and absence of cetyltrimethylammonium bromide (CTAB) have been studied. The binary complex formed at pH 5.6-6.0 in the absence of CTAB exhibits an absortion maximum at 360 nm with a molar absorptivity of 5.1 x 10(4) 1.mole(-1).cm(-1). The complex formed at pH 4.8-6.0 in the presence of CTAB has a molar absorptivity of 1.32 x 10(5) 1.mole(-1).cm (-1) at 400 nm, the wavelength of maximum absorption. Optimum conditions for complex formation were investigated and a rapid, sensitive and relatively selective method for the determination of up to approximately 70% of Mo in diverse alloys and steels is described. Small amounts of zirconium and tungsten interfere.     

Spectrophotometric determination of iron in highly alkaline solution with 4-hydroxy-1,10-phenanthroline

4-Hydroxy-1,10-phenanthroline forms a stable tris-chelate with iron(II) in the range of alkalinity from pH 10 to 2M sodium hydroxide, with molar absorptivity 1.19 x 10(4) l.mole(-1).cm(-1) at 545 nm. The determination of iron is performed by adding the phenanthroline, stannous chloride, and iron-free sodium hydroxide to the sample to give pH > 13; stannite is the active reductant. Beer's law is obeyed over the iron concentration range from 1 x 10(-5) to 8 x 10(-5)M. Advantages over existing methods are the use of stannous chloride instead of sodium dithionite, which avoids the problem of turbidity, and the stability of the iron(II) chelate towards oxidation by air. The conditional reduction potential at pH 11 for the iron(III)/iron(II) complex couple is 0.39 V.     

Spectrophotometric determination of samarium(III) with chrome azurol S in the presence of cetylpyridinium chloride

A sensitive, simple method for the determination of trace amounts of samarium by spectrophotometry is described based on the formation of the samarium-chrome azurol S (CAS) complex in micellar medium. The molar absorptivities of the complexes at pH 7.5 at 505 nm were 3.6x10(4) and 1.4x10(5) l mol(-1) cm(-1) for water media and cetylpyridinium chloride (CPC), respectively. Beer's law is obeyed from 0.05-2 mg l(-1) of samarium at 505 nm as Sm-CAS-CPC complex. Optimal conditions such as reagent amounts, and pH for the samarium determination were reported. The effects of foreign ions were also investigated. The proposed method was successfully applied to the determination of samarium contents in synthetic samples.     

Determination of nickel with 2-(2-quinolylazo)-5-diethylaminoaniline as a chromogenic reagent.

A sensitive, selective and rapid method for the determination of nickel based on a rapid reaction of nickel(II) with 2-(2-quinolylazo)-5-diethylaminoaniline (QADEAA) has been developed. In the presence of pH = 6.0 ammonia-ammonium chloride buffer solution and sodium dodecyl sulfonate (SDS) medium, QADEAA reacts with nickel to form a violet complex having a molar ratio of 1:2 (nickel to QADEAA). The molar absorptivity of the complex is 1.38 x 10(5) l mol(-1) cm(-1) at 595 nm. Beer's law is obeyed in the range of 0.01-0.4 microg/ml. This method had been applied to the determination of nickel with good results.     

Determination of submicrogram amounts of Mercury(II) with 5-(2'-carbomethoxyphenyl)azo-8-quinolinol in presence of anionic surfactant by derivative spectrophotometry

A new sensitive, rapid and selective method is proposed for the determination of mercury in submicrogram level. Mercury(II) forms an insoluble complex with 5-(2'-carbomethoxyphenyl)azo-8-quinolinol in aqueous medium at pH 4-4.8 which can be made soluble by the action of anionic surfactant. The dissolution of the complex results in an orange red colour which is stable for at least 20 hr. The molar absorptivity and Sandell's sensitivity are at 512 nm 8.00 x 10(4) l. mol(-1) . cm(-1) and 0.0025 mug/cm(2), respectively. Derivative spectrophotometry is used to achieve selectivity.     

Perxanthate determination in flotation solutions by ultraviolet spectrophotometry

Alkyl perxanthates (ROCSSO(-)) can be determined in solutions from flotation plants or other systems by direct ultraviolet spectrophotometry or after extraction into a solvent. Direct determination is preferred for visually clear solutions. In alkaline solution (pH > 8) at 348 nm perxanthates have a molar absorptivity of (1.042 +/- 0.013) x 10(4) l.mole(-1).cm(-1) and Beer's law holds up to 25 mg/l. The detection limit with a 1-cm cell is 0.2 mg/l. Interferences are few; nickelocyanide (>30 mg/l.) interferes slightly. After acidification to pH < 2, with an aqueous:organic phase-volume ratio of 1:1, more than 99% of the perxanthate is extracted into chloroform. In chloroform perxanthic acids have an apparent molar absorptivity of (5.47 +/- 0.09) x 10(3)l.mole(-1).cm(-1) at 302 nm. The absorbance of the chloroform extract at 302 nm is proportional to perxanthate concentration in the original aqueous phase up to 25 mg/l. The detection limit with a 1:1 phase-volume ratio and a 1-cm cell is 0.2 mg/l. Interferences include mercaptobenzothiazole (>1 mg/l.), sodium sulphite (>25 mg/l.) and cuprocyanide; xanthate interferes if it is not decomposed before extraction.     

Spectrophotometric determination of palladium after solid-liquid extraction with 1-(2-Pyridylazo)-2-naphthol at 90 degrees C

An effective spectrophotometric determination of palladium with 1-(2-pyridylazo)-2-naphthol (PAN) using molten naphthalene as a diluent has been studied. A green complex of palladium with PAN is formed at 90 degrees C. In the range of pH 1.5-7.5, the complex is quantitatively extracted into molten naphthalene. The organic phase is anhydrously dissolved in CHCl(3) to be determined spectrophotometrically at 678 nm against the reagent blank. Beer's law is obeyed over the concentration range of 0.5-10 ppm. The molar absorptivity and Sandell's sensitivity are 1.2 x 10(4) l mol(-1) cm(-1) and 0.0070 mg cm(-2), respectively. The optimum conditions for determination are obtained. The interferences of various ions are observed in detail. The method has been applied to the determination of palladium in synthetic samples.     

Spectrophotometric studies and application on the beta-type complex of Y-CPApK

The beta-type complex formed between yttrium and p-carboxychlorophosphonazo (CPApK) has been studied. It was found that Y-CPApK complex can give a maximum absorptivity in a buffer media of HAc-NaAc ranging from pH 3.5-4.3 and at a wavelength of 732 nm. Under the conditions employed, the molar absorptivity was found to be 7.72x10(4) l mol(-1) cm(-1) and the molar ratio of Y-CPApK was 1:2. The linear range was within 2-16 mug of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. The parameters which were related to the formation of the beta-type complex of Y-CPApK were discussed and a comparison of existing beta-type complexes between yttrium and the chlorophosphonazo reagents of chromotropic acid was made.     

Flotation-spectrophotometric determination of mercury in water samples using iodide and ferroin.

This paper describes a simple and highly selective method for separation, preconcentration and spectrophotometric determination of trace amounts of mercury. The method is based on the flotation of an ion-associate of HgI4(2-) and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and dissolved in acetonitrile to measure its absorbance. Quantitative flotation of the ion-associate was achieved when the volume of the water sample containing Hg(II) was varied over 50 - 800 ml. Beer's law was obeyed over the concentration range of 3.2 x 10(-8) - 9.5 x 10(-7) mol l(-1) with an apparent molar absorptivity of 1 x 10(6) l mol(-1) cm(-1) for a 500 ml aliquot of the water sample. The detection limit (n = 25) was 6.2 x 10(-9) mol l(-1), and the RSD (n = 5) for 3.19 x 10(-7) mol l(-1) of Hg(II) was 1.9%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of the almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic waste, and seawater samples was carried out by the present method and a well-established method of extraction with dithizone. The results were satisfactorily comparable so that the applicability of the proposed method was confirmed in encountering with real samples.     

Extraction-spectrophotometric determination of aluminium in river water with pyrocatechol violet and a quaternary ammonium salt

The simple removal of excess of co-extracted reagent in the solvent extraction of anionic metal complexes with a quaternary ammonium salt greatly improves the determination of aluminium with Pyrocatechol Violet (PV) and zephiramine (tetradecyldimethylbenzylammonium chloride). The exchange equilibrium constants for PV reagent and aluminium complex with four univalent anions (halides and nitrate) were determined when chloroform and 1,2-dichloroethane were used as extracting solvents. The constants were compared with those obtained with Pyrogallol Red. The method with PV and chloroform is suitable for the determination of micro-amounts of aluminium in river water. The apparent molar absorptivity of the aluminium complex in chloroform is 8.9 x 10(4) 1 mol(-1) cm(-1) at 587 nm. The limit of detection and precision achieved with the method are 3 mug l(-1) and within 4% respectively. A large excess of reagent can be used, and the ternary complex can be completely extracted over the pH range 5.5-10. Masking agents allow most interferences to be suppressed.     

Separation via flotation, spectrophotometric speciation, and determination of vanadium(IV) in wastes of power stations.

1-(2-Hydroxy-4-methoxybenzophenone)-4-phenylthiosemicarbazone (HMBPT) was investigated as a new reagent for the flotation of vanadium(IV). At pH approximately 1.5, vanadium(IV) forms a 1:1 pale-violet complex with HMBPT in aqueous solution. An intense clear violet layer was formed after flotation, by adding an oleic acid (HOL) surfactant. The composition of the float was 1:1 [V(IV)]:[HMBPT]. A highly selective and sensitive spectrophotometric procedure was proposed for the determination of microamounts of V(IV) as its floated complex. The molar absorptivities of the V(IV)-HMBPT and V(IV)-HMBPT-HOL systems were 0.4 x 10(4) and 0.12 x 10(5) L mol(-1) cm(-1) at 560 nm, respectively. The formation constants of the species formed in the presence and absence of HOL were 4.6 x 10(7) and 8.7 x 10(5) L mol(-1), respectively. Beer's law was obeyed up to 1 x 10(-4) mol L(-1) in the aqueous layer as well as in the oleic acid layer. The HMBPT-V(IV) complexes formed in the aqueous solution and scum layer were characterized by elemental analysis, infrared and UV spectrophotometric studies. The mode of chelation between V(IV) and HMBPT is proposed to be due to a reaction between the protonated bidentate HMBPT ligand and V(IV) through the S=C and N=C groups. Interferences from various foreign ions were avoided by adding excess HMBPT and/or Na2S2O3 as a masking agent. The proposed flotation method was successfully applied to the analysis of V(IV) in synthetic mixtures, wastes of power stations, simulated samples and in real ores. The separation mechanism is discussed.     

Rapid, selective, direct and derivative spectrophotometric determination of titanium with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone

A simple and sensitive spectrophotometric method is developed for the determination of titanium in aqueous medium. The metal ion forms a reddish brown coloured complex with 2,4-dihydroxybenzaldehyde isonicotinoyl hydrazone (2,4-DHBINH) in the pH range 1-7. The complex shows two absorption maxima, one at 430 nm and the other at 500 nm. The reagent shows appreciable absorbance of 430 nm and negligible absorbance at 500 nm at pH 1.5. Beer's law is obeyed in the range 0.09 to 2.15 mug ml(-1) of titanium(IV). The molar absorptivity and the Sandell's sensitivity of the method are 1.35 x 10(4) 1 mol(-1) cm(-1) and 0.0049 mug cm(-2), respectively. A method for the determination of titanium by first-order derivative spectrophotometry is also proposed. The methods have been employed successfully for the determination of titanium in several alloy and steel samples.